[OSM-dev] Anyway to split or simplify an .osm file from the command line?
frederik at remote.org
Sun Sep 20 15:30:40 BST 2009
John Smith wrote:
> The majority of Australian postcodes have been converted from shape
> files to osm files, however there is a couple of complex/big areas
> that I'm having trouble dealing with in JOSM as a result, is there a
> simple way to simplify these files from a command line util?
Let me speak bluntly: Have you been in touch with *anyone* who knows
something about OSM before you attempted this import?
One of the files you are trying to import has a node with more than
40.000 ways. Even if JOSM would handle it, the API would not accept it.
Even if teh API would accept it, you would basically sabotage any
attempt at mapping anything touching the boundary of that post code area
because they would be forced to download 4 MB of postcode area data even
if they just wanted a little stretch of road that happened to cross it.
Your ways are not tagged with anything. Did you plan to add the tags
manually in JOSM before uploading?
I have not checked this but given the ignorance that speaks from the
above, I very much assume that you have not undertaken any effort to
re-use nodes and ways; my guess is that where there is a boundary
between two post code areas, you will import every node twice, once as
part of post code area 1 and once as part of post code area 2... right?
This is an awful waste of space and not how we do things in OSM.
Please stop this import, take a deep breath, find out how to do it
right, and then do it properly.
Could the author(s) of shp2osm also please make sure that users of the
tool are educated about multipolygons and the maximum sizes of ways.
John, the following thread should have some information about how to
properly import a mesh of boundaries (which I believe is what you are
planning to do):
In short, you need to create "multipolygon" relations consisting of ways
with no more thane 2,000 members each, and where you have shared
boundaries these should be ONE way with ONE set of nodes, with the way
referenced by the two post code area multipolygon.
The thread also mentions the newly setup "imports support" working group
which you can contact for help if you want.
Please, folks, be more careful with imports. I'd rather *not* have post
code data than botched imports. Well-meaning as they are, they can
easily do more damage than any vandalism we have seen until now.
More information about the dev